Electrodes and process for making the same



Patented Dec. 17, 1929 UNITED STATES PATENT OFFICE GOLIN G. FINK, OF YONKERS, AND RUSSELL E. LOWE, OF NEW YORK, N. Y., ASSIGNORS TO BARIO METAL CORPORATION, OF NEW YORK. N. Y., A. CORPORATION OF DELA- 'WARCE ELECTRODES AND PROCESS FOR MAKING THE SAME No Drawing.

Our present invention relates to combinations of metals which are particularly adapted to resist the action'of free halogens, and particularly in' electrodes used in the electrolytic decomposition of.halogen salts. e will first describe the preferred form of our invention as. it would be applied to an anode used in the electrolysis of salt solutions and the processes by which such an anode is preferably made.

We first form an alloy of silver and lead with the percentage of silver preferably greater than that of the lead, say, 60 per cent of silver and 40 per cent lead although the lead may vary from about 25 to 75% with the silver varying from about 7 5 to 25%. This alloy is soft and ductile and has a high electrical conductivity and may be rolled or otherwise formed or shaped to form at least the body portion of the anode which will be contacted by the electrolytic bath.

We preferably coat the anode with a depolarizer which, in additionto decreasing the electrical resistance, will also serve to remove the corroding gas as rapidly as possible from the anode to minimize possible corrosion and, at the same time, will act as a protective coating for the anode alloy base. Preferably we use as such a depolarizer an oxide of one of the metals in the alloy forming the body portion of the anode. Thus with the anode formed of lead and silver, we preferably make the depolarizer of lead peroxide, because we have found that by so doing, the depolarizing coating will be maintained even when, after long usage, the anode alloy base is attacked by the gases and the electrolytic solution.

This coating of lead peroxide may be conveniently formed by first running the newly formed electrode as an anode in a halogen bath and afterward asan anode in an acid solution of lead nitrate until .acoating of lead peroxide of a desired thickness has been deposited on the anode.

The electrode thus formed has many advantages over the electrodes heretofore used in the electrolysis of halogen salts. Our electrode is relatively inexpensive, has hi h electrical conductivity, cannot be easily roken,

Application filed August 25, 1923. Serial No. 659,386.

may be readily shaped into any desired form and finally and particularly is attacked by the gases and the electrolyte only extremely slowly, thus insuring a long life for the electrode.

While preferably we use an alloy of lead and silver, it will be understood that any other metals, the halogen salts of which are diflicultly soluble in the electrolyte of the halogen salt baths, may be used. It will also be understood that three or more metals may be used as an alloy instead of the two which we have described as our preferred form. Thus manganese up to, say, 10 per cent may be used in the silver-lead alloy and (or) thallium up to, say, 20 per cent.

When manganese is one of the metals of the alloy, the depolarizing coating may be formed by running the anode first in a halogen salt bath and afterward as an anode in a formic acid solution of manganous sulphate containing sodium formate. This will produce the coating of manganese dioxide which will act as a depolarizer.

While we have described our alloy as applied to an electrode, it will be understood that it may also be used in any chemical apparatus in which surfaces are liable to be attacked by free halogens.

We claim:

1. In apparatus for the electrolysis of halogen salts, an electrode having a metallic body portion composed of an alloy containing lead and silver with the percentage of silver greater than the percentage of lead.

2. In apparatus for the electrolysis of halogen salts, an electrode having a metallic body portion composed of an alloy containing lead and silver with the percentage of silver greater than the percentage of lead, andd a depolarizing coating of peroxide of lea 3. In apparatus for the electrolysis of halogen salts, an electrode having a metallic body portion composed of an alloy containing lead, silver and manganese.

4. In apparatus for the electrolysis of halogen salts, an electrode having a metallic body portion composed of an alloy containing lead, silver and manganese, and a depolarizing coating comprising an oxide of one of the metals of the alloy.

5. The steps in the process of forming halogen-resisting electrodes, comprising forming the body portion of the electrode of an alloy containing at least two metals substantially all of the salts of which are difiicultly soluble in halogen salt solutions, then running the electrode as an anode in a 10 halogen salt electrolyte and then as an anode in an electrolyte containing a non-halogen salt of one of the metals of the body portion until a coatingof an oxide of such metal is deposited on the body portion.

v COLIN G. FINK.

RUSSELL E. LOWE. 

